The situation where the load changes in a certain way over time can be seen in many machines and machinery. This type of load typically occurs in machines that undergo periodic action, such as cranes, friction presses, crank presses, steel mills, etc. The lifting, transporting, releasing, and re lifting process of a crane can be considered as one working cycle. The crank press presses one workpiece, which is counted as one working cycle. The rolling mill completes a working cycle consisting of several processes for each type of steel rolled. These machines experience cyclic and repetitive changes in the load on their shafts according to their working cycles.
The characteristic of load changing over time is illustrated using a crawler excavator as an example. When the machine first starts to remove the tree stump, the stump does not move and the load reaches its maximum value. As the stump is slowly pulled up, the load gradually decreases until all the stumps are pulled up and the load drops to zero. Represents the relative load (as a proportion of the maximum load), and the horizontal axis represents the number of relative stress cycles (as a proportion of the total stress cycles). It is convenient to use a stepped load diagram to determine the equivalent load and equivalent stress cycle number.
The distribution of load along the wheel hub depends on the combined deformation of the wheel hub and shaft under external load. Due to the effect of the set of parts on the shaft, a portion of the load on the shaft is removed during operation, while increasing the stiffness of the shaft, which is beneficial for its operation.
However, it is difficult to calculate the load distribution under this combined deformation, not only because the deformation calculation of the assembled parts is complex, but also because it involves contact stress issues. It is not easy to determine the load distribution through experimental methods, therefore, so far there is no satisfactory method for calculating the load distribution at the hub and pinion joint, and it can only be estimated approximately